One method for treatment of a tympanic perforation uses a graft patch which is placed on the undersurface of the tympanic membrane after introducing the patch through the perforation. This grafting method belongs to the group of undersurface techniques. Because this surgical method is always performed through the external ear canal and the tympanic perforation, it minimizes surgical invasion and therefore is preferable. The grafting material of the patch in conventional methods is usually made of living human tissue, for example, temporalis fascia or subcutaneous connective tissue which is taken from the patient through an incision in his or her scalp during the operation.
In preparation of the tympanic membrane remnant for grafting, trimming of the perforation margin is performed by using a pick and a tiny cup forceps, and otherwise scoring is performed on the undersurface of the remnant membrane by inserting the head of a very tiny sharp-spoon, the tip of an angled pick or the tip of a curved injection needle through the perforation.
In order to fix the graft close to the undersurface of the tympanic membrane remnant, some gelatin sponge is packed in the tympanic cavity to support the graft temporally, or some fibrin glue is applied so that the graft adheres to the tympanic membrane remnant.
Generally speaking, a grafting technique should minimize its harm to the patient's body. In some prior methods, grafting material is obtained by making a new incision in some other area of the patient's body. This incision gives the patient additional pain and injury.
On the other hand, if artificial material, for example, lyophyrized dura as collagen fiber membrane is used, it increases the possibility of postoperative detachment because of its lack of vascularity. This usually results, in the whole graft falling off, or slit formation and subsequent graft failure. Therefore, it is hard to expect success of perforation closure with artificial grafting material.
For good blood circulation and to promote growth of fibroblast and capillary vessels in the graft, the contact of the graft with the vascular bed should be direct, tight and stable.
If absorbable gelatin sponge is packed in the tympanic cavity in order to support the graft temporally, the gelatin sponge irritates the mucosal lining of the tympanic cavity and induces hypersecretion and infection and otorrhea are apt to occur. The packing also interrupts immediate improvement of hearing after the operation as well.
If fibrin glue is used as an adhesive medium, supporting means is largely free of these problems. But the glue itself is apt to be dissolved by secretion in the tympanic cavity in the healing process. This brings about a loss of contact of the graft with the tympanic membrane remnant and often results in falling off of the graft.
There should also be a good blood supply to keep the reconstructed component viable. This requires that the mucosa at the back of the fibrous lamina propria around the perforation be entirely removed to provide a vascular bed for the undersurface grafting.
But trimming of the margin around the tympanic perforation cannot provide any suitable vascular bed, and, to make matters worse, it gets the perforation larger and increase the time of postoperative healing.
Scoring undersurface around the perforation removes the mucosal layer only partially in lines. Therefore, the graft cannot directly contact the vascular bed because of mucosal barrier. The fibroblast and capillary vessels can hardly enter into the collagen fiber network of the graft as a result.
Those are some of the inherent problems in the prior undersurface techniques and they lead to graft failure in eardrum perforation repair.